Category: Chemistry
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Chemical Property: Definition, Examples, and Meaning
Continue ReadingChemical Property Introduction
Anything which has mass in occupy space is called matter. Everything is around us is matter. A matter can be divided into two categories depending on the characteristics of a substance.
The properties of a substance are generally grouped into two categories which are Physical Properties and Chemical Properties.
Physical properties are defined as a characteristic of a substance which can be observed or measured without changing the composition of its matter. Further physical properties are classified into intensive and extensive property.
What is Chemical Property?
Chemical property refers to the characteristic of substance that undergoes change in its chemical structure. In simple terms, this property describes the ability of a substance to undergo a definite chemical change.
These properties are different from physical properties as chemical property can’t be observed by touching or seeing a substance.
On the other hand, Chemical Properties can only be distinguished when a material is in the process of being transformed into another substance.
For Example; Chemical property of iron is its ability to combine with oxygen to form iron oxide whose chemical name is rust.
Metals generally have a chemical property of reacting with acids. Hydrogen gas is produced when zinc reacts with hydrochloric acid and oxygen, this is also a chemical property.
Chemical Property Examples
Some of the common chemical properties include;
Heat of combustion: Heat of combustion is the heat released during the conversion process under standard conditions.
For example, combustion of methane with oxygen.
Toxicity: Toxicity is defined as the damage caused by the substance to animals, plants, and other organisms.
For instance, LED can damage the various parts of human body as it is a toxic substance and it can also damage heart, kidneys, and intestines.
Other examples of chemical properties include acidity, reactivity, flammability (Wood is an instance of flammable matter), oxidation states, type of chemical bonds etc.
Characteristics of Chemical Property
● Chemical properties are observed or measured when a system undergoes a chemical reaction or chemical change.
● Chemical properties are directly linked to the chemical bonds of the substance.
● This property is used to predict how the substances will react in different medium.
● The structure of a material changes entirely in chemical properties.
Chemical Property Uses
● Chemical properties of a substance are used to classify compounds and help us find their applications.
● Scientist also use these chemical properties to determine whether the given sample will participate chemical reaction or not.
● Chemical properties of a substance help us in its purification, separation from other chemical substances.
● Chemical properties unlike physical property are a characteristic that can only be observed when a given substance is being changed into different substance as a result of a chemical reaction or chemical change.
Chemical Change
● Chemical change is also known as a chemical reaction.
● In order to to identify a chemical property we must look for a chemical change.
● Chemical change results in one or more substances of totally different compositions from the original substances. Thus, it means that different elements or compounds are present at the termination of a chemical reaction.
● Reactants are the ingredients of a reaction and products are their result.
Reactants → Products
For instance, when an iron is exposed to water it becomes a mixture of hydrated iron oxides and hydroxides.
● Some examples of chemical changes include lightning of fireworks as fireworks consists of some metal nitrides and other chemicals constituting to burning compounds.
● Thus, when we let a firework combustion take place then this leads to formation of new substance and the release of light and heat thus, it is considered as a chemical change, The explosion of nitroglycerine is also a chemical change because the gases which are produced are of different kind from the novel substance.
● Burning, cooking, and rusting are all kinds of chemical changes because they produce new substances.
● Chemical changes are very vital in our lives. All new substances are shaped as a result of chemical changes such as digestion of food in our body, ageing of fruits, fermentation of grapes, etc., happen due to the result of chemical changes.
● Useful new materials, for example plastics and detergents, are produced as a result of chemical reactions/changes. Certainly, every new material is discovered by reviewing chemical changes of that particular substance.
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Physical Property: Definition, Examples, and Meaning
Continue ReadingPhysical Property Definition
Changes can be categorized into physical and chemical. Matter is made up of tiny particles and has both physical and chemical properties.
A chemical property is defined as the characteristic of a substance that can be observed in a chemical reaction.
For example heat of combustion, toxicity, acidity, reactivity etc.
Physical Property is defined as the characteristic of a substance that can be observed without changing the chemical nature of the substance such as its size, state of matter, colour, mass, density etc.
Some other physical properties include solubility, melting and boiling points etc.
The physical property of matter also includes Mellability which occurs when metal is moulded into thin sheets, for instance, silver is shiny metal and it can be moulded into thin sheets.
Hardness which is another physical property helps to determine how the element can be used.
Carbon in diamond is very hard whereas carbon in graphite is very soft.
Melting and boiling point is the physical property that is unique identifiers, especially of compounds.
Following are the most common physical properties that are used in selecting materials or substances Density implies the weight of the substance. Density is defined as mass divide by volume.
Melting point is defined as the minimum temperature required for the solid material to change into a liquid.
Colour is the reflective property of a material Boiling point is defined as the minimum temperature required for a liquid to change into a gas.
Physical Property Classification
There are two classes of physical properties which are
1. Extensive Physical Property
2. Intensive Physical Property
1. Extensive Physical Property
Extensive properties are those properties that depend on the size of the sample. Shape, volume and mass are extensive properties.
The properties like length,mass weight and volume that not only depend on the size but also depend on the quantity of the matter.
For instance, if we have two boxes made up of the same material one has the capacity of 6 litres and the other has the capacity of 12 litres then the box with 12-litre capacity will have more amount of matter as compared to that of 6-litre box.
2. Intensive Physical Property
Intensive properties are those properties that do not depend on the size or amount of matter in the sample.
Temperature, pressure and density is some of the examples of intensive properties other examples include colour, melting and boiling points as they will not change with the change in size as well as quantity of matter. The density of 1 litre of water or 1000 litre of water will remain the same as it is an intensive property.
Physical Change
Physical change takes place without any changes in the molecular composition of the substance. The same molecule is present in the substance throughout the changes.
Physical changes are related to the physical properties of a substance which are solid liquid and gas. During physical change the composition and the chemical nature of matter are not changed chemical property is not affected by the physical change of a substance.
The physical change includes a change in colour, solubility,change in the state of matter etc. Examples of physical change include melting an ice cube, dissolving sugar and water. Boiling water is also an example of physical change because the water vapour has the same molecular formula as that of liquid water.
To identify a physical change we have to look for a phase change for example if we freeze water into solid ice we can still melt the water again.
Physical Property Uses
Physical property is used to determine the appearance, texture, colour etc. of a substance thus, these physical properties are important as they help us to differentiate between different compounds.
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Homogeneous Mixtures: Examples, Definition, and Types
Continue ReadingHomogeneous Mixtures: Introduction
When 2 or more substances are mixed in any proportion, then this combination is defined as a mixture. Mixtures can be separated by physical methods such as evaporation, distillation, etc.
For example; salt and water, where 2 different components are mixed to form a mixture.
Mixtures can further be classified into homogenous and heterogeneous mixtures.
A Homogenous mixture is defined as the mixture where the composition is the same that is components are mixed uniformly.
Example; sugar and water.
A heterogeneous mixture is defined as the mixture where components are mixed non-uniformly, thus form 2 separate layers.
For example; soil and water are 2 different components that do not mix and thus form a layer and can be seen through a naked eye.
Homogeneous Mixtures
Homogeneous is derived from two words ‘homo’ meaning the same and geneos meaning ‘group/type’. Thus homogeneous means having the same or uniform composition.
A solution is a homogeneous mixture for example lemonade is a solution of lemon and water. The components of the solution are solute and solvent. The solute is dissolved in a solvent that is present in a larger quantity.
For example; a solution of sugar in water where sugar is the solutes taken in small quantity and water is the solvent taken in larger amounts.
Characteristics of Homogeneous Mixtures
The homogenous mixture/solution has only one phase that is solid, liquid and gas. Examples for the same are;
Solid homogeneous mixture: brass is an alloy that is made from metal copper (Cu) and zinc (Zn).
Liquid homogeneous mixture: a saline solution that is the mixture of water and salt.
Gas homogenous mixture: air is a mixture of different gases such as oxygen, carbon dioxide, nitrogen, and many more gases present in smaller amounts in the environment.
The size of particles of the solution is smaller than one nanometer thus homogenous mixtures do not show the Tyndall effect and cannot be seen with the naked eye.
The solute particles do not settle down when left uninterrupted, thus, a solution is stable.
Homogeneous Mixtures Examples
1. Salt and water.
2. Alcohol and water.
3. Steel is an alloy made from copper and iron.
4. Bronze is an alloy which is a mixture of copper and tin.
5. Natural gas is a mixture of methane and other gases.
Types of Solutions
Dependent upon the dissolution of the solute in the solvents, solutions can be categorized into the following;
A supersaturated solution comprises a large amount of solute that can be dissolved by the solvent where the extra solute will crystallize quickly at a particular temperature. The most prevalent example is sodium acetate which is a supersaturated solution.
An unsaturated solution is a solution in which a solvent can dissolve any more solute at a given temperature.
A saturated solution can be defined as a solution in which a solvent is not capable of dissolving any further solute at a given temperature thus it means that the maximum amount of solute has been dissolved and further no more solutes can be dissolved in the given solvent.
Factors Affecting Solubility
The quantity of solute that can be dissolved in a solvent to form a saturated solution depends following factors given;
Temperature: Solubility is directly proportional to temperature thus it increases with temperature. For example, we can dissolve much more salt in hot water as compared to cold water.
Pressure: Increasing pressure can vigor more solute into solution. This is usually use to dissolve gases into liquids.
Chemical Composition: The nature of the solute and solvent and the existence of other chemicals in a solution affects its solubility. For example, we can dissolve much more sugar in water as compared to salt.
Solution Form
The solutions are of two forms, depending on the solvent if its water or not.
Aqueous solution: When a solute is dissolved in water then this type solution is called an aqueous solution.
For example; salt in water and sugar in water
Non-aqueous solution: When a solute is dissolved in a solvent other than water, then this type of solution is called a non-aqueous solution.
For Example; iodine in carbon tetrachloride, sulphur in carbon disulfide.
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Pure Substances: Definition, Examples, and Difference
(more…) Continue ReadingPure Substances
Anything which occupies space and has mass is called matter. The matter is divided into two categories which are; Mixtures and Pure substances.
1. Pure Substances
Pure substances are defined as substances made up of only one kind of atom or molecule.
Pure substances also have fixed shapes and structures.
Pure substances are further classified into elements and compounds.
For example; gold metal
2. Mixtures
Mixtures are also called impure substances because it is composed of different kinds of components.
Mixtures are further divided into two categories which are a homogeneous mixture and heterogeneous mixture.
Example; water and sand, salt and water.
Difference Between Pure Substances and Mixtures
Pure Substances Mixtures Pure substances are made up of a single kind of particles The mixture is composed of two or more different substances. Pure substances can be classified into elements and compounds Mixtures are classified into homogenous and heterogenous They have a definite set of properties They don’t have a definite set of properties Components of pure substances cannot be separated by physical methods Components of the mixture can be separated by physical methods such as evaporation, etc. For example; hydrogen gas For example; oil and water Properties of Pure Substances
• Pure substances are in most cases homogeneous in nature containing only one form of atoms or molecules.
• Those substances especially have a constant or uniform composition throughout.
• Pure substances have static boiling and melting points.
Pure Substances Examples
All elements are commonly pure materials. Some of them encompass gold, copper, oxygen, chlorine, diamond, etc.
Compounds including water, salt or crystals, baking soda among others are also grouped under pure substances.
Depending on who you communicate to, homogeneous mixtures can also be taken into consideration as examples of pure materials.
Examples of homogeneous combinations include vegetable oil and air.
Heterogeneous mixtures are not considered pure substances.
Examples of homogenous mixtures that aren’t pure substances include gravel, a mixture of salt and sugar, etc.
Elements
A pure substance that has only one kind of atom and also cannot be broken down into two or more simpler substances by the physical or chemical method is called an element. Thus, when we break down gold, we still get gold. Thus, it is an element.
Properties of Elements
• An element is homogeneous; it’s a pure substance, made from a single form of atoms. As an instance, iron and silver are the product of only iron and silver atoms. Consequently, they’re elements.
• Elements cannot be broken down into more simpler substances by any physical or chemical processes such as heat, chemical reactions.
• Elements have sharp melting and boiling factors.
• Elements are categorized as metals, non-metals, and metalloids.
(a) Metals
Metals are the elements that voluntarily lose an electron to shape a positive ion or a cation.
For example; Gold, silver, copper, iron, potassium, etc.
– Metals have lustre. For Example; Gold.
– Metals are accurate conductors of warmth and energy. As metals have unfastened electrons in them, they may be able to behavior warmness and electricity. Example: Copper
– Metals are malleable, which means that it’s easy to mallet them into thin sheets. Instance: Aluminum
– Metals are ductile, meaning they can be drawn into wires.
– Metals are sonorous. They deliver a ringing sound when they’re hit via a tough iron rod. For Example; copper.
– Nearly all metals are solids at room temperature. Exception; Sodium and potassium are tender metals. Tungsten is a bad conductor of electricity.
(b) non-Metals
Non – metals are those elements voluntarily gain an electron(s) to shape a negative ion or anion.
Examples encompass Hydrogen, Oxygen, Iodine, etc.
– Non-metals exist as solids, liquids, and gases. Instance: Silicon and carbon are solids; bromine is a liquid; chlorine, fluorine, and oxygen are gases.
– Non-metals are non-lustrous, which means they have a dull look. Instance: The surfaces of sulfur and phosphorus do not gloss.
– Generally, non-metals have very low density. For Example, Oxygen and nitrogen are lighter than air.
– They’re not malleable.
– Non-metals, besides carbon, aren’t ductile.
– They’re terrible conductors of electricity. exception; graphite is a superb conductor of strength.
– Non-metals have low melting and boiling factors.
(c) Metalloids
The factors which have intermediate characteristics among the ones of metals and non-metals are known as metalloids. They are amphoteric.
– Metalloids react both with acids and bases. Examples encompass boron, silicon, and germanium.
Compound
A natural substance, essentially composed of two or greater elements and chemically mixed in a set share is called a compound. Consequently, water is a compound. It has two elements, hydrogen, and oxygen, mixed in a set ratio.
Properties of a Compound
– A compound is homogeneous in nature, made up of identical types of molecules.
– The additives of a compound can be separated by using chemical and electrochemical strategies. Thus, water may be broken down into hydrogen and oxygen through electrolysis.
– A compound have a fixed composition.
– A compound has a sharp melting and boiling factor.
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States of Matter: Definition and the Five...
Continue ReadingStates of Matter: Introduction
The term matter is defined as anything that occupies space and has mass. The matter can neither be created nor be destroyed. Various forms of matter exist in nature and these are solid, liquid, and gas. The fourth state of matter is plasma but it does not exist in our everyday life.
A states of matter is only a way to describe the behavior of atoms and molecules in a substance.
What is States of Matter?
A substance can take on different physical forms depending on various things such as temperature, pressure, and substance`s properties. The physical form is commonly called the state of matter. The states of matter are also called phases.
There are four common states of matter and it has been described in Figure 1.
Figure 1: The different states of matter
1. Solid State
The solid is one of the state of matter, where the molecules are tightly packed and are held together by strong forces.
The molecules in the case of solids are not able to move freely however they can vibrate at their fixed positions.
The solids have a fixed shape and size.
The rate of diffusion in solids is low and density is high.
Examples of solid include metal and ceramic bowls.
Based on the arrangement of solid molecules, the solids can further be divided into crystalline and amorphous.
(a) Crystalline Solid State
The crystalline solid state of matter is a periodic arrangement of fixed and long-range order of atoms/ molecules in all three dimensions.
Among the common examples are rock salt, sugar, metal keys, etc.
(b) Amorphous Solid State
The amorphous solid state of matter is a periodic arrangement of a short range of atoms/ molecules in all three dimensions.
Common examples are window glass, cotton candy, etc.
2. Liquid State
In liquids, the forces between the molecules are weaker than the solids.
Particles are fairly close together but can move around freely.
The liquids have an indefinite shape and can adapt to the shape of the container in which it has been kept.
The volume of liquid is fixed and the rate of diffusion in liquid is comparatively higher than that of solids.
The examples commonly include cola, coffee, tea, etc.
3. Gaseous State
This state of matter can be differentiated by low density and viscosity.
great expansion & contraction with changes in pressure and temperature, capacity to diffuse readily; and the tendency to become distributed homogeneously throughout any container.
The shape of the gas is not fixed.
The particles of gas have weak or no bonds.
The kinetic energy of gas molecules is very high as intermolecular forces are small.
The air we breathe is composed of gaseous states of many elements of which only oxygen is choosen by our body.
Plasma State
The matter of plasma is composed of atoms/ molecules, under the condition of standard pressure & temperature (STP) matter.
It has electrons that can orbit the atomic nucleus.
The shape and volume of plasma are not fixed.
If the temperature is very high, the electrons in the valence shell acquire enough kinetic energy to escape the atom. Therefore the plasma has very high kinetic energy.
The plasma produces the magnetic fields and sturdily responds to the electromagnetic field.
Plasma also possesses exclusive properties as free electrical charges cause it to be electrically conductive.
Examples of plasma are the illuminated state such as lighting, electric sparks, and some types of flames.
Phase Change
Phase changes occurs ,when the temperature or pressure change of a system takes place,.
When the temperature or pressure increases, the contact between the molecules increases.
Similarly, when the temperature decreases, it is much easier for molecules and atoms to settle into a more rigid structure.
Below represents the numerous phase changes.
– Freezing
– Melting
– Vaporization
– Condensation
– Sublimation
Change of State between Solid and Liquid
(a) Freezing
The method by which the substance changes from the liquid phase to the solid phase. The temperature at which any substance freezes, is called the freezing point.
For example the freezing of water to become solid ice.
(b) Melting
The process by which solid changes to liquid is called melting. The example here is when ice cubes from the freezer are placed in a warm room, the ice would absorb energy from the warmer air around them.
This absorption of energy would facilitate them to overcome the forces of attraction holding them together and enabling them to slip out of the fixed position that they held as ice.
Change of state Between Liquids and Gases
(a) Vaporization
Bubbles of water vapor form in the boiling water because particles of liquid water gain sufficient energy to completely overcome the force of attraction between them and change to the gaseous state.
Thus, the bubbles rise through the water and escape from the vessel as steam. The process of vaporization happens through two methods and that is evaporation and boiling.
The method in which a liquid boils and changes to gas is termed vaporization. The temperature at which a liquid boils. For example; boiling water to become steam, salt is recovered from seawater through this process.
(b) Condensation
When hot water interact with cooler surfaces such as the mirror, it chills and loses energy. The cooler water particles no longer have the energy to overcome the forces of attraction between them.
Together they form droplets of liquid water. This process in which a gas changes to liquid form is defined as condensation.
Example; Fog in the Air, Visible Breath in Cold Conditions, Clouding a Mirror, Steamy Rest room Mirror.
Change of state Between Solids and Gases
(a) Sublimation
The process in which solids directly change to gases is defined as sublimation. This occurs when solids absorb enough energy to overcome the forces of attraction between them.
For example; Dry ice is a case of solids that undergo sublimation, Snow and ice can sublime in the wintertime without melting, Mothballs sublime, Frozen foods sublime and ice crystals are found inside of the box.
(a) Deposition
A deposition is defined as the process in which a gas changes directly to a solid without going through the liquid state.
Examples of deposition in nature include frost forming on the ground and cirrus clouds forming high in the atmosphere, beaches, deltas, glacial moraines,sand dunes and salt domes in strictly cold temperatures form frost on windows because the water vapor in the air comes into contact with a window and proximately forms solid ice without even forming liquid water.
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Classification of Matter: Definition, Types, and Examples
Continue ReadingWhat is Matter?
When we study the term chemistry, it is often described as the state of matter. The concept of matter includes substances, compounds, elements, mixtures etc.
The matter shows some of the properties such as smell, colour etc. The substances can undergo changes which commonly include physical and chemical properties.
Physical properties commonly include shape, size, colour, and mass. Chemical properties include flammability.
Definition of Matter
The definitions of the following terms such as;
Matter: The term matter is commonly defined as anything that has mass and occupies space. The matter is further classified as solid, liquid and gas.
Substance: It is defined as the matter which is homogenous and of which all parts are alike. The substance can be homogenous and heterogenous.
Elements: The elements are pure substances that cannot be decomposed into simpler substances by chemical means. Some of the examples include gold, sulphur and iron.
Compounds: The compounds are pure substances that are composed of two or more elements.
Mixture: This is defined as a matter which consists of two or more substances mixed. A mixture can be homogenous or heterogeneous.
Homogenous mixtures are those that are not seen by the naked eye for example salt dissolves in water whereas heterogeneous mixtures are those that can be seen by the naked eye, for example, several different components.
Classification of Matter
The matter is classified as mixtures and substances. The mixture is further classified as homogenous and heterogeneous. The substances are further classified as elements and compounds.
Figure below will give the relationship between the concepts.
Mixture
A mixture is defined as a material that is made up of two or more different substances that are mixed but not combined chemically. An example of a mixture is sand and water.
The mixture is further classified into two parts and which are homogenous and heterogeneous.
I. Homogenous Mixture
The homogenous mixture is defined as a mixture of two or more substances where the different components cannot be visually distinguished.
If we take an example of a homogenous mixture then it would be a solution in sports drinks, consisting of water, sugar, colouring, flavouring, and electrolytes mixed uniformly.
Every sip of soft drink tastes the same because each sip contains the same amount of substances as mentioned above.
There are a few other examples of homogenous mixture that will include air, maple syrup. gasoline and solution of salt in water.
II. Heterogeneous Mixture
The heterogeneous mixture is defined as a mixture with a varying composition . The example includes Italian dressing.
The composition of Italian dressing can vary because it may be prepared by mixing different amounts of oil, vinegar, and herbs.
It is not uniform throughout the mixture—one drop may be mostly vinegar, whereas a different drop may be mostly oil or herbs because the oil and vinegar isolate and the herbs settle.
Substances
As per the definition in chemistry, substances are a form of matter that has a constant chemical composition and characteristic properties. The separation of components will only be possible when there is a breaking of chemical bonds.
The chemical substances can be solid, liquid or gas. The change in temperature or pressure can cause substances to shift between the different states of matter.
The substances are often called as pure as it separates them from the term mixture. An example of a substance is pure distilled water as it has always the same properties and the same ratio of hydrogen to oxygen.
The substances are further divided into two parts and that are elements and compounds.
Elements
The elements can be defined as a pure substance that consists of only one type of atom. The elements are divided into metals, metalloids and non-metals.
If we take a look at the periodic table in below Figure, the left side of the periodic table consists of metals that are often conductive to electricity, malleable, shiny and sometimes magnetic.
Examples of metals are aluminium, iron, copper etc. The right side of the periodic table consists of non-metals. The characteristic of non-metals includes not conductivity, not malleable, dull and not magnetic. The examples include carbon and oxygen.
As per the data of November 2011, 118 elements have been identified and out of 118, only 98 are known to occur naturally on the earth.
The most abundant elements on the earth are Hydrogen and Helium. All the known chemical matter is composed of these elements. The chemical matter constitute nearly about 15% of the matter in universe.
Compounds
The chemical compounds have a unique and defined structure a fixed ratio of atoms held together in a defined spatial arrangement by chemical bonds.
The few characteristics of chemical compounds can be that the molecular compounds are held together by covalent bonds.
Another characteristic is the salts are held together by ionic bonds or by metallic bonds and the complexes can also be held together by coordinate covalent bonds.
Pure chemical elements are not called chemical compounds even if they consist of diatomic or polyatomic molecules.
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Orbital Hybridization: sp1, sp2, and sp3 Hybridization,...
Continue ReadingWhat is Hybridization?
The concept of hybridization was introduced by scientist pauling. He defined hybridization as redistribution of the energy of orbitals of individual atoms to give new orbitals of equivalent energy. This new orbitals formed are called hybrid orbital.
Features of Hybridization
• Number of hybrid orbitals = number of atomic orbital that get hybridized.
• Hybridized orbitals have equal energy and shape.
• Hybridization takes place with the orbitals of valence shell.
• Hybridisation does not take place in the isolated atom.
Types of Hybridization
sp Hybridization
When one s and one p orbital in same main shell mix together to give new hybrid, orbital called sp hybridised orbital. Forms linear molecules with 180 angle.
Example: all compounds of beryllium such as BeF2, BeCl2
sp2 Hybridization
One s + two p orbitals of the same shell = 3 equivalent orbital , new orbitals formed are called sp2 hybrid orbitals.
Angle: 120
Shape: trigonal planar shape
Example: All the compounds of Boron such as BCl3
sp3 Hybridization
1 s orbital + 3 p orbitals of same shell = 4 new equivalent orbital. new orbitals formed are called sp3 hybrid orbitals.
Angle: 109°28’ with one another Shape Tetrahedral
Example: ethane (C2H6), methane.
sp3d Hybridization
3p orbitals + 1d orbital = 5 orbitals of equal energy. Angle.
Equatorial orbitals: 3 hybrid orbitals lie in the horizontal plane inclined at an angle of 120 Axial orbitals.
The remaining 2 orbitals lie in the vertical plane at 90 degrees plane Shape : trigonal bipyramidal geometry
Example: Phosphorus pentachloride (PCl5)
sp3d2 Hybridization
1s + 3p + 2d orbitals = 6 identical hybrid orbitals.
Shape: octahedron.
Angle: 90 degrees to one another.
Example: sulfur hexafluoride SF6
sp3d3 Hybridization
1s +3p+3d =5 orbital of same element mix and recast to form hybrid orbitals
Shape: pentagonal bipyramidal geometry
Example: IF7
Concept of Hybridization of Carbon Atom
sp Hybridization: When Carbon is bound to two other atoms with the help of two double bonds or one single and one triple bond.
Example: Hybridization of CO2.
sp2 Hybridization: When carbon atom bonding takes place between 1 s-orbital with two p orbitals then the formation of two single bonds and one double bond between three atoms takes place.
Example: Hybridization of graphite
sp3 Hybridization: When the carbon atom is bonded to four other atoms.
Example: Hybridization of CH4 (Methane)
How to Determine Hybridization?
Hybridization of Nitrogen in Ammonia, NH3
Step 1: Write the Lewis structure
The valency of nitrogen is 3.
Thus, it forms 3 bonds with three hydrogen atoms.
There is also a lone pair on nitrogen.
Step 2: Calculate number of sigma (σ) bonds
Nitrogen in ammonia is bonded to 3 hydrogen atoms.
Number of sigma bonds are = 3.
Step 3: Calculate number of lone pairs
Number of lone pairs on nitrogen atom = (v – b – c) / 2
= (5 – 3 – 0) / 2 = 1 lone pair
There are 5 balance electrons in nitrogen atom before bond formation.
Step 4: Calculate steric number of nitrogen atom
Steric number = number of σ bonds + number of lone pairs
Thus, 3 + 1 = 4
Step 5: Give hybridization and shape of molecule
Nitrogen in ammonia is sp3 hybridization.
The shape is pyramidal.
Hybridization and Shape of XeF4
Step 1: Calculate the number of sigma (σ) bonds
Number of sigma bonds formed by xenon = four as it is bonded to only 4 fluorine atoms.
The valency of fluorine = one.
Step 2: Calculate number of lone pairs
The number of lone pairs on xenon atom = (v – b – c) / 2 = (8 – 4 – 0) / 2
Step 3: Calculate the steric number of central atom
Steric number = number of σ-bonds + number of lone pairs = 4 + 2 = 6
Step 4: Allocate hybridization and shape of molecule
The hybridization is sp3d2.
Thus, Structure is based on octahedral geometry
Hence, Shape is square planar.
Hybridization and Shape of SO2
Step 1: Write the Lewis structure
Sulfur’s valency may be 2 or 4 or 6.
Oxygen’s valency = one.
Each oxygen makes two bonds with sulfur atom.
One is sigma bond and the second one is pi bond.
The total number of bonds formed by sulfur with two oxygen atoms = four.
Step 2: Calculate number of sigma (σ) bonds
The number of sigma bonds formed by sulfur atom = two
As it is bonded to two oxygen atoms.
Step3: Calculate number of lone pairs
The number of lone pairs on sulfur atom is = (v – b – c) / 2 = (6 – 4 – 0) / 2; Thus 1.
Number of valence electrons in sulfur is 6.
Total number of bonds including sigma and pi bonds is = 4.
Step 4: Calculate steric number of central atom
Steric number = no. of σ-bonds + no. of lone pairs = 2 + 1 Thus 3
Step 5: Give the hybridization and shape of molecule
The hybridization is sp2.
Structure is built on trigonal planar geometry with one lone pair.
Shape is = angular.
Steric Number
If steric number is 4, then it is sp3
If steric number is 3 then it is sp2
If steric number is 2 then it is sp
C1 – SN = 3 (three atoms connected), thus sp2
C2 – SN = 3 (three atoms connected), thus sp2
O4 – SN = 3 (1 atom + 2 lone pairs), thus sp2
O5 – SN = 4 (2 atoms + 2 lone pairs), thus sp3
C6 – SN = 4 (4 atoms), thus it is sp3
C7 – SN = 4 (4 atoms), thus it is sp3
N8 – SN = 4 (3 atoms + 1 lone pair), thus it is sp3
C9 – SN = 2 (2 atoms), thus it is sp
C10 – SN = 2 (2 atoms) thus it is sp
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Atomic Number: Definition, Examples, and Facts
Continue ReadingAtomic Number: Introduction
Atoms are the vital building blocks of all matter and are composed of protons, neutrons, and electrons. The atoms are electrically neutral, the number of positively charged protons is equal to the number of negatively charged electrons.
Subsequently neutrons do not affect the charge, the number of neutrons is not reliant on the number of protons and will differ even amongst atoms of the same element.
History of Atomic Number
In 1910, Henry Gwyn-Jeffreys Moseley gave the concept of atomic number that was evolved from historic research. While experimenting on several chemical elements with X-rays.
He observed the pattern formed by reflected rays. After this experiment, he discovered that the wavelength of the reflected X-rays decreased in a regular predictable pattern with the increase in atomic mass.
According to his hypothesis, the regular variation in wavelength from element to element was triggered by an increase in the positive charge on atomic nuclei in going from one element to the next-heavier element.
After the discoveries made by Moseley, another scientist named Dmitri Mendeleev in 1850 proposed a new considerate understanding of the periodic law.
Mendeleev said that the properties of elements differ in a regular and expectable pattern when the elements are organized according to their atomic masses.
His theory was somewhat correct as the periodic table on this basis had a most important flaw. Certain pairs of elements seem to be misplaced when arranged according to their masses.
Various difficulties disappear when the atomic number rather than atomic mass is used to construct the periodic table. An element`s chemical properties rest on the number and arrangement of electrons in its atoms.
The number of electrons in an atom, is determined by the nuclear charge. Thus, the number of protons in a nucleus governs the chemical properties of an element.
What is Atomic Number?
The atomic number is represented by the letter Z . It is defined as the number of protons in the nucleus of each atom of that element.
The one characteristic that makes each element unique compared to all other elements is the number of protons. The elements are different because of their atomic number.
For example, any atom with an atomic number of 8 (its nucleus contains 8 protons) is an oxygen atom, and an atom with a different number of protons would be a different element.
Figure below showing the periodic table that displays all of the known elements and is arranged in order of increasing atomic number. In the below figure of the periodic table, the atomic number is displayed above the elemental symbol.
Figure: The periodic table is classified elements by atomic number
For example, Hydrogen at the upper left of the table has an atomic number of 1. Each hydrogen atom has one proton in its nucleus. Subsequent on the table is helium, whose atoms have two protons in the nucleus. Lithium atoms have three protons, beryllium atoms have four protons, and so on.
Meanwhile atoms are neutral, the number of electrons in an atom is equal to the number of protons. Hydrogen atoms normally have one electron that occupies the space outside of the nucleus.
Helium having two protons, will have two electrons. The count of proton will always be equal to an atom’s atomic number. This value will not vary unless the nucleus decays or is been bombed.
Mass Number
Several experiments have shown that the majority of the mass of an atom is been concentrated in its nucleus that is composed of protons and neutrons.
The mass number is represented by the letter A. It is also defined as the total number of protons and neutrons in an atom.
Table below shows the data from the first six elements from the periodic table. If we take the example of helium here. The atomic number of helium is 2 so that means it has 2 protons in its nucleus. And the nucleus also contains 2 neutrons.
So, the mass number of helium is 4. So this concludes helium atom contains 2 electrons as the number of electrons is equal to the number of protons.
Another example taken here can be of Lithium that has three protons and four neutrons and here the mass number will be equal to seven.
Table: The atoms of the first six elements
Name Symbol Atomic Number (Z) Protons Neutrons Electrons Mass Number (A) Hydrogen H 1 1 0 1 1.01 Helium He 2 2 2 2 4.00 Lithium Li 3 3 4 3 6.94 Berylium Be 4 4 5 4 9.01 Boron B 5 5 6 5 10.18 Carbon C 6 6 6 6 12.01 Atomic Number Calculation
Therefore, the formula can be made from this, by knowing the mass number and an atomic number of an atom we can determine the number of neutrons present in that atom by subtraction.
Number of neutrons = Rounded Mass number – Atomic number
So, this shows how can we calculate the atomic number and mass number of a given element.
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